Some X-ray shutters are capable of terminating the exposure of an object to X-rays, for the case that the capacities of power supply cables to an X-ray tube still supply current or power to the X-ray tube, even after a programmed exposure time. For this purpose, an exposure controller is connected to a first solenoid which, prior to or during the excitation of the X-ray tube, pulls a radiopaque shutter slide made of lead, tungsten, or uranium against the tensile force of a spring into an open position in which the shutter is held by means of a detent latch of a second, de-energized solenoid. In the open position, a radiation window in the shutter allows X-rays to pass through. After a controller has initiated generation of the X-ray radiation, and as soon as a sensor detects a preset irradiation threshold value, the controller excites the de-energized solenoid, which removes the detent latch from the shutter. The mass of the shutter and the force of the spring are selected in such a way that the shutter may be moved from the open position into a closed position in approximately 1/5000 second in order to rapidly interrupt the X-ray radiation.
A problem with the known shutter devices, in which the shuttering of the beam path takes place by means of a slide which is introduced in a direction transverse to the beam path, is that the spring responsible for the required rapid actuation of the shutter may fatigue or break over time. In addition, the system comprising the spring, slide, and detent latch is complex, and due to the linear motion of the slide requires a relatively large installation space. To be able to keep the size of the slide, and thus its mass, small, it must be situated close to the radiation source, since at that location the cross-sectional surface of the radiation to be shuttered is small. Lastly, for the spring-actuated linear motion of the slide, a damping means is necessary in order to avoid rebound of the slide at the end position, so that ultimately, the dimensioning of the spring, slide, and damping element always represents a compromise solution.
Some rotary shutters are shiftable between a first position in which an X-ray beam path is blocked, and a second position in which the X-ray beam path is open. A closed position indicator having optical sensors can detect a reliable rotation of the rotary shutter into the first or second position, by means of a magnetic drive. The known rotary shutter and the control of the position of the shutter are complex.